1. Field of the Invention
The invention relates to a tapered roller bearing.
2. Description of Related Art
As depicted in FIG. 7, a tapered roller bearing 90 includes an inner ring 91, an outer ring 93, a plurality of tapered rollers 95, and an annular cage 96. The inner ring 91 has a tapered inner ring raceway surface 92. The outer ring 93 has a tapered outer ring raceway surface 94. The tapered rollers 95 roll on the inner ring raceway surface 92 and the outer ring raceway surface 94. The cage 96 holds the tapered rollers 95 at intervals along a circumferential direction. The inner ring 91 has a cone back face rib portion (hereinafter, referred to as a large rib portion) 97 protruding radially outward on a large diameter side of the inner ring 91. The large rib portion 97 has an annular rib surface 99 that contacts a roller large end face 98 of each of the tapered rollers 95.
Rotation of the tapered roller bearing 90 brings the roller large end face 98 of each tapered roller 95 into sliding contact with the rib surface 99 of the inner ring 91. Thus, to reduce frictional resistance (sliding frictional resistance) between the roller large end face 98 and the rib surface 99, the roller large end face 98 has a convex curved surface with a predetermined curvature radius, and the rib surface 99 has a recessed curved surface with a predetermined curvature radius (see, for example, Japanese Utility Model Application Publication No. 115-75520 (JP 5-75520 U)).
For the tapered roller bearing 90 as described above, there has been no specific definite guideline that specifies how to set the curvature radius of the roller large end face 98 of each tapered roller 95 and the curvature radius of the rib surface 99 of the inner ring 91. Thus, a very effective reduction in frictional resistance may not be expected depending on the values of the curvature radii of the roller large end face 98 and the rib surface 99.